Heretofore, single loop deacceleration warning systems have permited drivers to indicate deacceleration while downshifting: U.S. Pat. Nos. 4,105,994, 4,162,384, 4,158,833 all to Chicoine, Ross U.S. Pat. No. 3,821,701 and Ellison U.S. Pat. No. 3,501,742. The switches were in direct series with the braking lamps, and were exposed to arcing by the heavy lamp current. As these systems aged, oxide buildup on the contacts caused a high impedance connection therebetween. The resulting voltage loss across the switch reduced the voltage appearing across the braking lamps, causing a loss in lamp intensity. Variations in driver contact pressure, further aggravated the unreliability impedance of the oxidized contacts. In addition, the rate of operation between drivers varied producing corresponding variations in the lamp intensity and activation period. A rapid flash is less noticeable by other drivers. If the flash period is too short, the braking lamps are prematurely deactivated and fail to reach an operating brightness.
Prior art double loop warning systems such as Shames U.S. Pat. No. 3,911,394, Mulrooney U.S. Pat. No. 2,787,778, and Lipe U.S. Pat. No. 3,891,986 provided isolation to varying degrees.
All of the prior art systems were subject to intentional and inadvertent activation during times other then deacceleration.